The present inventive concept herein relates to optical communication systems, and more particularly, to an optical line terminal registering an optical network terminal having overlapping serial numbers and a method of registering an optical network terminal thereof.
A passive optical network (hereinafter it is referred to as ‘PON’) provides a wideband to subscribers and accommodates various multi protocols. A PON has a structure connecting various optical network terminals (hereinafter it is referred to as ‘ONT’) or various optical network units (hereinafter it is referred to as ‘ONU’) to an optical line terminal (hereinafter it is referred to as ‘OLT’) through a passive device using a point to multi-point method.
In the PON system having a structure like that, the OLT transmits a declining data frame to various ONTs and the various ONTs transmit an upward data frame to the OLT only in the allocated time. In the PON system, the OLT performs a certification procedure for transmitting an upward traffic to the various ONTs which are connected.
A certification operation in the OLT may be divided into a registration operation registering a serial number of the ONTs and a ranging operation performing a ranging. In a single network, ONTs located at the same distance or at a different distance may have the same serial number. ONTs which are located at physically same distance and have the same serial number are allocated the same optical network unit_IDentifier (hereinafter it is referred to as ‘ONU_ID’) from the OLT. Thus, in the ranging operation, ONTs having the same serial number respond at the same time. As response messages between the ONTs having the same serial number collide with each other, there was a problem that the certification operation cannot be normally performed.
In the case that ONTs located at a different distance have the same serial number, response messages between the ONTs do not collide with each other. However, since ONTs having the same serial number are allocated the same compensation value, an upward traffic may be transmitted in time which the OLT does not allow. There was a problem that data cannot be normally transmitted or received due to the upward traffic transmitted in the time which the OLT does not allow.